Orthogonal Frequency Division Multiplexing Receiver

1. An orthogonal frequency division multiplexing (OFDM) receiver, comprising: an offset compensator configured to receive a digital input signal and a sampling offset, and to convert the digital input signal into a baseband signal in accordance with the sampling offset; a fast Fourier transform (FFT) block configured to perform an FFT operation of the base band signal output from the offset compensator and to output a corresponding FFT result; a control unit configured to generate OFDM symbol information and a plurality of control signals based on the FFT result; a channel impulse response estimation block configured to periodically generate receiving channel impulse response information of a receiving channel based on the FFT result; and a sampling offset estimation block configured to generate the sampling offset based on the FFT result, the receiving channel impulse response information, the OFDM symbol information, and the plurality of control signals.

2. The OFDM receiver of claim 1 , wherein the channel impulse response estimation block comprises: an equalizer configured to compensate for a carrier distorted by the receiving channel with respect to the FFT result; an inverse discrete Fourier transform (IDFT) block configured to execute an IDFT of an output signal of the equalizer and to output a corresponding IDFT result; and a channel impulse estimator configured to generate the receiving channel impulse response information based on the IDFT result.

3. The OFDM receiver of claim 1 , wherein the sampling offset estimation block comprises a carrier controller configured to generate pilot carrier information for classifying pilot carriers of an OFDM symbol into first pilot carriers and second pilot carriers according to positions and a cumulative symbol count indicating the number of OFDM symbols, with respect to which sampling offset estimation is performed, based on the OFDM symbol information.

4. The OFDM receiver of claim 3 , wherein the sampling offset estimation block further comprises a phase calculation unit configured to perform complex multiplication of a result of performing the FFT operation of OFDM symbols as many in number as the cumulative symbol count and a result of delaying the FFT result for a predetermined OFDM symbol interval, to classify a result of the complex multiplication into the first pilot carriers and the second pilot carriers based on the pilot carrier information, and to generate a phase difference between a sum of phases of the first pilot carriers and a sum of phases of the second pilot carriers.

5. The OFDM receiver of claim 4 , wherein the phase calculation unit comprises: a delay unit configured to delay the FFT result for the predetermined OFDM symbol interval; a complex multiplier configured to perform complex multiplication of the FFT result and the delayed FFT result; and a phase accumulation unit configured to classify the complex multiplication result into the first pilot carrier and the second pilot carriers based on the pilot carrier information, and to generate an accumulated phase value of the first pilot carriers and an accumulated phase value of the second pilot carriers.

6. The OFDM receiver of claim 5 , wherein the phase calculation unit further comprises: a comparison block configured to compare the FFT result with a predetermined first reference value and to output a comparison result; and a scaler configured to scale the comparison result based on a scale signal.

7. The OFDM receiver of claim 6 , wherein the comparison block comprises: a bit selector configured to select predetermined upper bits from the FFT result and to output the selected upper bits; and a comparator configured to compare the first reference value with the selected upper bits and to output the comparison result.

8. The OFDM receiver of claim 5 , wherein the phase calculation unit further comprises: a valid bit selector configured to select valid bits of the accumulated phase value of the first pilot carriers and valid bits of the accumulated phase value of the second pilot carriers, and to output the selected valid bits; a phase calculator configured to calculate the sum of phases of the first pilot carriers and the sum of phases of the second pilot carriers based on the selected valid bits; and a phase detector configured to generate a phase difference between the sum of phases of the first pilot carriers and the sum of phases of the second pilot carriers.

9. The OFDM receiver of claim 8 , wherein the number of the selected valid bits is the same as the number of input bits of the phase calculator, and the phase calculator calculates the sum of phases of the first pilot carriers and the sum of phases of the second pilot carriers by performing a COrdinate Rotation Digital Computer (CORDIC) algorithm on the selected valid bits.

10. The OFDM receiver of claim 3 , wherein the sampling offset estimation block further comprises an offset estimation unit configured to perform a forgetting factor algorithm on a phase difference between the sum of phases of the first pilot carriers and the sum of phases of the second pilot carriers, and to generate a sampling offset value.

11. The OFDM receiver of claim 10 , wherein the offset estimation unit comprises: a first multiplier configured to multiply the phase difference by a first weight; and a forgetting loop configured to generate the sampling offset value based on an output signal of the first multiplier, a delayed sampling offset value for a predetermined symbol interval, and a second weight.

12. The OFDM receiver of claim 11 , wherein the forgetting loop comprises: an adder configured to add the output signal of the first multiplier and a result of multiplying the delayed first sampling offset value for the predetermined symbol interval by the second weight, and to generate the sampling offset value; a delay unit configured to generate the delayed sampling offset value for the predetermined symbol interval based on the sampling offset value; and a second multiplier configured to generate the result of multiplying the delayed sampling offset value for the predetermined symbol interval by the second weight.

13. The OFDM receiver of claim 11 wherein the offset estimation unit further comprises a forgetting loop controller configured to initialize an accumulated value of the forgetting loop when the accumulated value is greater than a predetermined maximum value.

14. The OFDM receiver of claim 11 , wherein the offset estimation unit further comprises a forgetting loop controller configured to initialize an accumulated value of the forgetting loop when a predetermined period of time elapses after the forgetting loop is initialized.

15. The OFDM receiver of claim 3 , wherein the sampling offset estimation block further comprises an offset estimation unit configured to generate the sampling offset based on a sampling offset value and the receiving channel impulse response information.

16. The OFDM receiver of claim 15 , wherein the offset estimation unit comprises: a window offset conversion unit configured to convert a window drift value included in the receiving channel impulse response information into a unit of sampling offset; an adder configured to add the converted window drift value and the sampling offset value; and a loop filter configured to filter an output signal of the adder to generate the sampling offset.

17. The OFDM receiver of claim 16 , wherein the offset estimation unit further comprises a loop filter controller configured to initialize an accumulated value of the loop filter when the sampling offset is greater than a predetermined maximum value.

18. The OFDM receiver of claim 16 , wherein the window offset conversion unit comprises: a conversion controller configured to exclude window drift values beyond a predetermined range from sampling offset estimation; and an offset converter configured to convert the window drift value into the unit of sampling offset, and to output the converted window drift value to the adder.

19. An orthogonal frequency division multiplexing (OFDM) receiver comprising: a sampling offset estimation block configured to generate a sampling offset based on a result of performing a fast Fourier transform (FFT) operation of a receiving signal, receiving channel impulse response information of a receiving channel, and OFDM symbol information and a plurality of control signals which are generated from a result of the FFT operation; and an offset compensator configured to compensate for the sampling offset of the receiving signal, to convert the receiving signal into a baseband signal, and to output the baseband signal.

20. The OFDM receiver of claim 19 , wherein the sampling offset estimation block comprises: a carrier controller configured to generate pilot carrier information for classifying pilot carriers of an OFDM symbol into first pilot carriers and second pilot carriers according to positions and a cumulative symbol count indicating the number of OFDM symbols, with respect to which sampling offset estimation is performed, based on the OFDM symbol information; a phase calculation unit configured to perform complex multiplication of the result of performing the FFT operation of OFDM symbols as many in number as the cumulative symbol count and a result of delaying the result of the FFT operation for a predetermined OFDM symbol interval, to classify a result of the complex multiplication into the first pilot carriers and the second pilot carriers based on the pilot carrier information, and to generate a phase difference between a sum of phases of the first pilot carriers and a sum of phases of the second pilot carriers; a first offset estimation unit configured to perform a forgetting factor algorithm on the phase difference between the sum of phases of the first pilot carriers and the sum of phases of the second pilot carriers, and to generate a first sampling offset value; and a second offset estimation unit configured to generate the sampling offset based on the first sampling offset value and the receiving channel impulse response information.

21. The OFDM receiver of claim 20 , wherein the second offset estimation unit comprises: a window offset conversion unit configured to convert a window drift value included in the receiving channel impulse response information into a unit of sampling offset; an adder configured to add the converted window drift value and the first sampling offset value; and a loop filter configured to filter an output signal of the adder to generate the sampling offset.

22. The OFDM receiver of claim 21 , wherein the second offset estimation unit further comprises a loop filter controller configured to initialize an accumulated value of the loop filter when the sampling offset is greater than a predetermined maximum value.

23. The OFDM receiver of claim 21 , wherein the window offset conversion unit comprises: a conversion controller configured to exclude window drift values beyond a predetermined range from sampling offset estimation; and an offset converter configured to convert the window drift value into the unit of sampling offset, and to output the converted window drift value to the adder.